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Search Results: 1 - 10 of 5818 matches for " Andre-Claude Clapson "
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Multi-wavelength environment of the Galactic globular cluster Terzan 5
Andre-Claude Clapson,Wilfried Domainko,Marek Jamrozy,Michal Dyrda,Peter Eger
Physics , 2011, DOI: 10.1051/0004-6361/201015559
Abstract: Terzan 5 is a Galactic globular cluster exhibiting prominent X-ray and gamma-ray emission. Following the discovery of extended X- ray emission in this object, we explore here archival data at several wavelengths for other unexpected emission features in the vicinity of this globular cluster. Radio data from the Effelsberg 100 metre telescope show several extended structures near Terzan 5, albeit with large uncertainties in the flux estimates and no reliable radio spectral index. In particular, a radio source extending from the location of Terzan 5 to the north-west could result from long-term non-thermal electron production by the large population of milli-second pulsars in this globular cluster. Another prominent radio structure close to Terzan 5 may be explained by ionised material produced by a field O star. As for the diffuse X-ray emission found in Terzan 5, its extension appears to be limited to within 2.5 arcmin of the globular cluster and the available multi-wavelength data is compatible with an inverse Compton scenario but disfavours a non-thermal Bremsstrahlung origin.
Evidence for VHE emission from SNR G22.7-0.2 region with H.E.S.S
Hélène Laffon,Bruno Khélifi,Francois Brun,Fabio Acero,Jérémie Méhault,Gerd Pühlhofer,Peter Eger,Marek Jamrozy,Arache Djannati-Ata?,Andre-Claude Clapson,for the H. E. S. S. collaboration
Physics , 2011,
Abstract: Observations of the supernova remnant G22.7-0.2 in the field of view of W41 with the H.E.S.S. telescope array have resulted in evidence for a very high energy (VHE) gamma-ray emission from the direction of the object. The emission region is spatially coincident with molecular clouds visible in 13CO data, suggesting a hadronic origin of the TeV emission, although other scenarios brought by X-ray observations with the XMM-Newton satellite are also discussed. The latest results obtained on this SNR with H.E.S.S. and associated multi-wavelength information are presented here.
Description and Performance of a Novel Concept “Single Level” Ceramic Chip Carrier
Andre de Keyser,Claude Delautre,Guy Nameche
Active and Passive Electronic Components , 1983, DOI: 10.1155/apec.10.317
Cardiovascular Risk Reduction in Diabetes in Sub-Saharan Africa: What should the Priorities be in the Absence of Global Risk Evaluation Tools?
Andre Pascal Kengne,Alfred Kongnyu Njamnshi,Jean Claude Mbanya
Clinical Medicine : Cardiology , 2008,
Abstract: Background: The growing burden of type 2 diabetes in Sub-Saharan Africa (SSA) and related cardiovascular complications call for vigorous actions into prevention. Comprehensive cardiovascular risk evaluation is important for the success of such actions.Methods: We have reviewed 3 currently existing sets of recommendations for cardiovascular prevention in diabetes in SSA. Distribution of major risk factors and patterns of reported cardiovascular outcomes are used to suggest orientations for cardiovascular prevention in diabetes in this region. Papers and reports published over the period 1990 to 2007 were used.Results: Existing guidelines share some similarities, but also have areas of inconsistencies. They are generally adaptations of existing guidelines, focused more on individual risk factors, and are not usually backed-up by local evidence. They all have a projection on blood pressure lowering. This focus is supported by the high prevalence of hypertension among people with diabetes in SSA. Blood pressure and tobacco smoking are the modifiable risk factors accessible to evaluation and interventions on a wide scale in SSA. Appropriate blood pressure control will have a major impact on stroke (the commonest cardiovascular disease) through a reduction of the cerebrovascular risk, and to a lesser extent on coronary heart disease and total deaths in diabetes in this region.Conclusions: In the absence of global risk evaluation tools, the use of blood pressure lowering as a primary focus of cardiovascular prevention strategies is relevant for SSA. However, there is a need to set-up diabetes and stroke registers to monitor outcomes and generate tools for accurate risk prediction and management in diabetes in this region.
Observational Signatures of Galactic Winds Powered by Active Galactic Nuclei
Jesse Nims,Eliot Quataert,Claude-Andre Faucher-Giguere
Physics , 2014, DOI: 10.1093/mnras/stu2648
Abstract: We predict the observational signatures of galaxy scale outflows powered by active galactic nuclei (AGN). Most of the emission is produced by the forward shock driven into the ambient interstellar medium (ISM) rather than by the reverse shock. AGN powered galactic winds with energetics suggested by phenomenological feedback arguments should produce spatially extended 1-10 keV X-ray emission of 10^(41-44) erg/s, significantly in excess of the spatially extended X-ray emission associated with normal star forming galaxies. The presence of such emission is a direct test of whether AGN outflows significantly interact with the ISM of their host galaxy. We further show that even radio quiet quasars should have a radio luminosity comparable to or in excess of the far infrared-radio correlation of normal star forming galaxies. This radio emission directly constrains the total kinetic energy flux in AGN-powered galactic winds. Radio emission from AGN wind shocks can also explain the recently highlighted correlations between radio luminosity and the kinematics of AGN narrow-line regions in radio quiet quasars.
INCAS Bulletin , 2011, DOI: 10.13111/2066-8201.2011.3.1.8
Abstract: The problem developed in this paper is encountered in airplane aerodynamics and concernsthe influence of long life longitudinal wake vortices generated by wing tips or by external obstaclessuch as reactors or landing gears. More generally it concerns 3D bodies of finite extension in crossflow. At the edge of such obstacles, longitudinal vortices are created by pressure differences inside theboundary layers and rotate in opposite senses. It can constitute a danger to another aircraft that fliesin this wake, especially during takeoff and landing. In this case the wake vortex trajectories andstrengths are altered by ground interactions. This study presents the results of a Large EddySimulation of wake vortex in ground effect providing the vorticity flux behavior.
Comparison of Biotinylated Monoclonal and Polyclonal Antibodies in an Evaluation of a Direct Rapid Immunohistochemical Test for the Routine Diagnosis of Rabies in Southern Africa
Andre Coetzer,Claude T. Sabeta,Wanda Markotter,Charles E. Rupprecht,Louis H. Nel
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0003189
Abstract: The major etiological agent of rabies, rabies virus (RABV), accounts for tens of thousands of human deaths per annum. The majority of these deaths are associated with rabies cycles in dogs in resource-limited countries of Africa and Asia. Although routine rabies diagnosis plays an integral role in disease surveillance and management, the application of the currently recommended direct fluorescent antibody (DFA) test in countries on the African and Asian continents remains quite limited. A novel diagnostic assay, the direct rapid immunohistochemical test (dRIT), has been reported to have a diagnostic sensitivity and specificity equal to that of the DFA test while offering advantages in cost, time and interpretation. Prior studies used the dRIT utilized monoclonal antibody (MAb) cocktails. The objective of this study was to test the hypothesis that a biotinylated polyclonal antibody (PAb) preparation, applied in the dRIT protocol, would yield equal or improved results compared to the use of dRIT with MAbs. We also wanted to compare the PAb dRIT with the DFA test, utilizing the same PAb preparation with a fluorescent label. The PAb dRIT had a diagnostic sensitivity and specificity of 100%, which was shown to be marginally higher than the diagnostic efficacy observed for the PAb DFA test. The classical dRIT, relying on two-biotinylated MAbs, was applied to the same panel of samples and a reduced diagnostic sensitivity (83.50% and 90.78% respectively) was observed. Antigenic typing of the false negative samples indicated all of these to be mongoose RABV variants. Our results provided evidence that a dRIT with alternative antibody preparations, conjugated to a biotin moiety, has a diagnostic efficacy equal to that of a DFA relying on the same antibody and that the antibody preparation should be optimized for virus variants specific to the geographical area of focus.
Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows
Philip F. Hopkins,Paul Torrey,Claude-Andre Faucher-Giguere,Eliot Quataert,Norman Murray
Physics , 2015,
Abstract: We use hydrodynamic simulations to study the interaction of realistic active galactic nucleus (AGN) feedback mechanisms (accretion-disk winds & Compton heating) with a multi-phase interstellar medium (ISM). Our ISM model includes radiative cooling and explicit stellar feedback from multiple processes. We simulate radii ~0.1-100 pc around an isolated (non-merging) black hole. These are the scales where the accretion rate onto the black hole is determined and where AGN-powered winds and radiation couple to the ISM. Our primary results include: (1) The black hole accretion rate on these scales is determined by exchange of angular momentum between gas and stars in gravitational instabilities. This produces accretion rates of ~0.03-1 Msun/yr, sufficient to power a luminous AGN. (2) The gas disk in the galactic nucleus undergoes an initial burst of star formation followed by several Myrs where stellar feedback suppresses the star formation rate per dynamical time. (3) AGN winds injected at small radii with momentum fluxes ~L/c couple efficiently to the ISM and have a dramatic effect on the ISM properties in the central ~100 pc. AGN winds suppress the nuclear star formation rate by a factor of ~10-30 and the black hole accretion rate by a factor of ~3-30. They increase the total outflow rate from the galactic nucleus by a factor of ~10. The latter is broadly consistent with observational evidence for galaxy-scale atomic and molecular outflows driven by AGN rather than star formation. (4) In simulations that include AGN feedback, the predicted column density distribution towards the black hole is reasonably consistent with observations, whereas absent AGN feedback, the black hole is isotropically obscured and there are not enough optically-thin sight lines to explain observed Type I AGN. A 'torus-like' geometry arises self-consistently because AGN feedback evacuates the gas in the polar regions.
Constraining the dynamical importance of hot gas and radiation pressure in quasar outflows using emission line ratios
Jonathan Stern,Claude-Andre Faucher-Giguere,Nadia L. Zakamska,Joseph F. Hennawi
Physics , 2015,
Abstract: Quasar feedback models often predict an expanding hot gas bubble which drives a galaxy-scale outflow. In many circumstances the hot gas is predicted to radiate inefficiently, making the hot bubble hard to observe directly. We present an indirect method to detect the presence of a hot bubble using hydrostatic photoionization models of the cold (10^4 K) line-emitting gas. These models assume that the cold gas is in pressure equilibrium with either the hot gas pressure or with the radiation pressure, whichever is larger. We compare our models with observations of the broad line region (BLR), the inner face of the dusty torus, the narrow line region (NLR), and the extended NLR, and thus constrain the hot gas pressure over a dynamical range of 10^5 in radius, from 0.1 pc to 10 kpc. We find that the emission line ratios observed in the average quasar spectrum are consistent with radiation-pressure-dominated models on all scales. On scales <40 pc a dynamically significant hot gas pressure is ruled out for an average quasar spectrum, while on larger scales the hot gas pressure cannot exceed six times the local radiation pressure. In individual quasars, ~25% of the objects exhibit narrow line ratios that are inconsistent with radiation-pressure-dominated models by a factor of ~2, though in these objects the hot gas pressure is also unlikely to exceed the radiation pressure by an order of magnitude or more. The upper limits we derive on the hot gas pressure imply that the instantaneous gas pressure force acting on galaxy-scale outflows falls short of the time-averaged force needed to explain the large momentum fluxes \dot{p} >> L_AGN/c inferred for galaxy-scale outflows in luminous quasars. This apparent discrepancy can be reconciled if the optical quasars observed today previously experienced a buried, fully-obscured phase, (abridged)
Generating Net Forces from Backgrounds of Randomly Created Waves  [PDF]
Claude Gauthier
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.516158
Abstract: We examine the possibility of generating net forces on concave isolated objects from backgrounds consisting of randomly created waves carrying momentum. This issue is examined first for waves at the surface of a liquid, and second for quantum vacuum electromagnetic waves, both in relation with a one-side-open rectangular structure whose interior embodies a large number of parallel reflecting plates. Using known results about the Casimir-like effect and the original Casimir effect for parallel plates, we explain why and how such rectangular hollow structures should feel net oriented forces. We briefly describe real systems that would allow testing these theoretical results.
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